1. Field of the Invention
This invention relates to traffic light signals for controlling the flow of traffic on roads and highways.
2. Discussion of Relevant Art
Numerous traffic signal devices have been proposed in the past. One type of such device includes a housing having four walls with lights disposed in each of the walls. A centrally located rotating element sequentially illuminates the appropriate light for controlling traffic flow. Examples of this type of mechanism are shown in U.S. Pat. No. 1,466,809, issued Sept. 4, 1923, to Strong, U.S. Pat. No. 1,757,050, issued May 6, 1930, to Johnson, and U.S. Pat. No. 1,758,481, issued May 13, 1950, to Torrence. Additionally, some of the proposed traffic signals include light change indicators. For instance, U.S. Pat. No. 2,020,610, issued Nov. 12, 1935, to Johns includes gas tube signalling element having extensions which are illuminated in fractional parts, additively or subtractively, to visibly indicate the time remaining between differing illumination patterns of the traffic signal. U.S. Pat. No. 2,021,954, issued Nov. 26, 1935, to Campion, shows a traffic signal wherein rotating shutters having arcuately shaped slots are disposed over opposed warning tubes to progressively cover and uncover the warning tubes thereby indicating the time left before the light changes.
However, none of the above mentioned patents provides a scheme to insure positive mechanical synchronization between light changing circuitry and light change indicators on traffic lights having portions facing in all directions at an intersection. Such positive synchronization is necessary to insure smooth traffic flow and should be effected through mechanical interconnections for maintaining synchronization over a long period of time.